A New View of the Dwarf Spheroidal Satellites of the Milky Way from VLT FLAMES: Where Are the Very Metal-poor Stars?

Helmi, Amina; Irwin, M. J.; Tolstoy, E.; Battaglia, G.; Hill, V.; Jablonka, P.; Venn, K.; Shetrone, M.; Letarte, B.; Arimoto, N.; Abel, T.; Francois, P.; Kaufer, A.; Primas, F.; Sadakane, K.; Szeifert, T.
Referencia bibliográfica

The Astrophysical Journal, Volume 651, Issue 2, pp. L121-L124.

Fecha de publicación:
11
2006
Número de autores
16
Número de autores del IAC
0
Número de citas
192
Número de citas referidas
150
Descripción
As part of the Dwarf galaxies Abundances and Radial-velocities Team (DART) program, we have measured the metallicities of a large sample of stars in four nearby dwarf spheroidal galaxies (dSph's): Sculptor, Sextans, Fornax, and Carina. The low mean metal abundances and the presence of very old stellar populations in these galaxies have supported the view that they are fossils from the early universe. However, contrary to naive expectations, we find a significant lack of stars with metallicities below [Fe/H]~-3 dex in all four systems. This suggests that the gas that made up the stars in these systems had been uniformly enriched prior to their formation. Furthermore, the metal-poor tail of the dSph metallicity distribution is significantly different from that of the Galactic halo. These findings show that the progenitors of nearby dSph's appear to have been fundamentally different from the building blocks of the Milky Way, even at the earliest epochs. Based on FLAMES/GIRAFFE observations collected at the European Southern Observatory, proposal 171.B-0588.